Concurrent software programs are known to be prone to having software bugs, including bugs that result from the concurrent nature of the programs. In general, concurrency bugs occur when instructions are scheduled in an order not envisioned by the programmer. Concurrency software bugs are thus those that appear only on particular thread schedules. Many concurrent bugs are difficult to find because they are often dependent upon rare thread schedules.
A concurrent software program contains one or more threads of control, (referred to simply as “threads” hereinafter). In specific circumstances, these threads may refer to processes, threads within a process, processors in the computer hardware, and/or nodes in a distributed system. Common names for concurrent threads of control include, but are not limited to, threads, processes, nodes, agents, tasks and components,
A general goal of concurrency testing is to effectively identify which schedules, of the exponentially many possible schedules, are those in which concurrency bugs appear. Known testing methods involve various forms of stress testing, in which the program being tested is run for days or even weeks under heavy loads with the hope of hitting buggy schedules. This is a slow and expensive process. Moreover, any bugs that are found via stress testing are difficult to reproduce and/or debug.